In UMTS (Universal Mobile Telecommunications System) networks, for the purpose of improving spectral efficiency, peak data rates and the like, by adopting HSDPA (High Speed Downlink Packet Access) and HSUPA (High Speed Uplink Packet Access), it is performed exploiting maximum features of the system based on W-CDMA (Wideband Code Division Multiple Access). For the UMTS network, for the purpose of further increasing spectral efficiency and data rates, reducing delay and the like, Long Term Evolution (LTE) has been studied (Non-patent Document 1).
In Release-8 LTE (hereinafter, referred to as Rel. 8-LTE), as distinct from W-CDMA, as a radio access scheme, a scheme based on OFDMA (Orthogonal Frequency Division Multiplexing Access) is used in downlink. Meanwhile, a scheme based on SC-FDMA (Single-Carrier Frequency Division Multiple Access) is used in uplink.
The OFDMA scheme is a multicarrier transmission scheme for dividing a frequency band into a plurality of narrow frequency bands (subcarriers), and mapping data to each subcarrier to perform communications. In this OFDMA scheme, high-speed transmission is achieved by orthogonalizing subcarriers on the frequency axis to arrange densely, and it is expected to increase spectral efficiency.
The SC-FDMA scheme is a single-carrier transmission scheme for dividing the frequency band for each terminal to transmit using different frequency bands among a plurality of terminals. In this SC-FDMA scheme, it is possible to reduce interference between terminals readily and effectively and to further reduce fluctuations in transmission power, and this scheme is thereby preferable from the viewpoints of lower power consumption in the terminal, enlargement of coverage and the like.
In the above-mentioned LTE (Rel. 8-LTE) scheme system (LTE system), using variable bands ranging from 1.4 MHz to 20 MHz, it is possible to achieve transmission rates of maximum 300 Mbps in downlink and about 75 Mbps in uplink. Moreover, in the UMTS network, for the purpose of further increasing the wide-band and high speed, successor systems to LTE have been studied (for example, LTE Advanced (LTE-A)).
In the LTE-A scheme system (LTE-A system), with the aim of further improving spectral efficiency, peak throughput and the like, assignments of frequencies with a wider band than in LTE are studied. Further, in LTE-A, (for example, Rel. 10), it is one of requirements to have backward compatibility with LTE. Therefore, to LTE-A are introduced techniques (carrier aggregation (CA) techniques) for performing communications using a transmission band having a plurality of base frequency blocks (component carriers (CCs)) each having a bandwidth usable in LTE.